The present invention relates to an information distribution system which securely distributes contents such as music, and particularly relates to an authoring system which authors, by encryption for copyright protection, content data to be distributed through a computer program and a storage medium, an authoring key generator which generates a key for authoring, an authoring device which encrypts content data to author it, and an authoring method therefor, and also to a data supply device, information terminal and information distribution method which enable content data to be securely downloaded onto a storage medium such as a memory stick.
In recent years, with the spread of information networks such as the Internet, there have been suggested methods for the construction of an information distribution system which distributes various types of information such as music data, image data (still and animated), and game programs (hereinafter, such information is collectively called “content”) through a network to users. To realize such an information distribution system, it is a prerequisite to guarantee the protection of the copyright in each content. In other words, there is always the risk of large volumes of digital content data being copied. For this reason, several copyright protection techniques for preventing illegal copies of contents have been developed.
Generally, it is said that two encryption stages are necessary in order to prevent a content for distribution from being illegally copied. The first encryption stage is a stage in which, in order to protect the content from illegal copying in the course of its distribution, the content is encrypted during authoring. The second encryption stage is a stage in which, when a user writes the content into his or her storage device through an information terminal such as a kiosk terminal, it is encrypted to prevent later illegal copying.
Regarding these stages, in a conventional content distribution service, the encryption method for authoring is different from that for writing. Therefore, when writing the content into the user's storage device, the content must first be decrypted and again encrypted. This is time consuming. Here, another disadvantage is that the problem of security arises because the content decrypted during writing is temporarily raw data.
Further, in conventional information distribution systems, the content writing module does not have the function of license authentication, so the content is vulnerable in a situation where the module is stolen. Namely, it is possible to make digital copies of large volumes of content data from a stolen writing module.
Another problem of conventional information distribution systems is that protection of the authoring process is less effective and anyone who manages to obtain a copy of the specification for the authoring process can do authoring of the content.
Further, in conventional information distribution systems, if the content is music data, even when the user is an authorized user and going to move it into another medium after downloading it into his/her storage device, he/she cannot move it without sound quality deterioration.
Besides, in conventional information distribution systems, if the content is music data, only music and its title can be recorded into an MD or other medium; so-called fringe data such as jacket pictures and song lyrics cannot be recorded therein and the user has to print out the fringe data on a printer.